Density and refractive index of TiO2 films prepared by reactive evaporation

Abstract Thin amorphous films of titania were prepared by reactive evaporation at 300°C and at various pressures and deposition rates. The refractive index n and the thickness of the films were determined from transmission spectra. The density ρ of the films decreases when the mean free path length during deposition becomes smaller than the distance between source and substrate. A formula to describe the experimental data for n as a function of ρ is given. A Clausius–Mosotti analysis of n confirms the results of one group of the existing controversial literature. It is, however, shown that the often used classical Lorentz–Lorenz plot is generally not appropriate for experimental data obtained on thin films due to their inhomogeneous nature.